Boreas Inc.

Massachusetts Institute of Technology

James A Crunkleton

Joseph L Smith, Jr

Frederick James Cogswell

Anthony G Liepert

Gregory R Gallagher

A system for providing a cold environment which has a number of cooling stages with variable displacement volumes into which input fluid from a compressor flows in an input channel to and from the displacement volumes and output fluid flows in an output channel to the compressor. Volume changers vary the volumes of the displacement volumes and input fluid flowing to a first set of displacement volumes is pre-cooled by regenerative heat exchange and counterflow heat exchange and input fluid flowing to the final displacement volume is pre-cooled primarily by counterflow heat exchange. The volume changer at at least one of the stages is thermally decoupled from the input and output channels.

Cryogenic refrigeration apparatus

A technique for producing a cold environment in a refrigerant system in which input fluid from a compressor at a first temperature is introduced into an input channel of the system and is pre-cooled to a second temperature for supply to one of at least two stages of the system, and to a third temperature for supply to another stage thereof. The temperatures at such stages are reduced to fourth and fifth temperatures below the second and third temperatures, respectively. Fluid at the fourth temperature from the one stage is returned through the input channel to the compressor and fluid at the fifth temperature from the other stage is returned to the compressor through an output channel so that pre-cooling of the input fluid to the one stage occurs by regenerative cooling and counterflow cooling and pre-cooling of the input fluid to the other stage occurs primarily by counterflow cooling.

A technique for producing a cold environment wherein warm fluid, e.g. at room temperature, from a compressor, is introduced under pressure into an input channel which is directly coupled to a displacement volume, the fluid being precooled in the input channel to a temperature lower than that of the input fluid. Fluid in the inner channel at or near the displacement volume is periodically pressurized to a high pressure. The displacement volume is then expanded so that the high pressure fluid flowing into the expanded volume is decreased from such high pressure to a substantially lower pressure, the temperature thereof being reduced to a substantially lower temperature for producing the cold environment. The low pressure, low temperature fluid flows into an output channel, preferably via a suitable valve and surge volume, for flow in the output channel at a substantially constant pressure. A direct heat exchange is provided between the input and output channels to provide the precooling of the input fluid and a warming of the fluid in the output channel to a temperature relatively close to, but below, the temperature of the input fluid. The warmed fluid exiting from the output channel is supplied to the compressor when it is compressed for re-introduction into the input channel.

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Cambridge, MA, United States of America

James A Crunkleton